This invention relates generally to sewing machines and more particularly is concerned with an auxiliary feed mechanism associated therewith.
The industrial sewing machine industry has consistently sought ways by which an auxiliary feeding action may be placed upon the workpiece as the latter is fed through the stitching point of the machine. This is especially required when joining multiple layers of material or when it is necessary to reposition a workpiece that has been displaced from its normal course of travel. As disclosed in the above identified application, that portion of the workpiece immediately rearward of the presser foot is displaced from its normal path of travel by a rear ejector system. However, to assure the manufacture of an acceptable garment it is necessary to guide this displaced portion of the workpiece back to its normal path so that the remainder of the workpiece remains unaffected. As is apparent if the auxiliary feed mechanism of the machine has a feed rate velocity equal to the feed rate velocity of the feed mechanism of the machine the material that has been displaced will remain in that path of travel unless some outside force is applied thereto to return same to its normal path of travel. In addition to the above, it is desirous in some sewing operations to aid the feed mechanism of the machine in continually advancing the workpiece through the work station and to continually run after the machine stops in order to pull the material through the machine. It is also a common desire in some sewing operations to gather or stretch the fabric plies and then be able to come back to the normal condition rapidly without any further readjustment of the auxiliary feed machanism.
It is known in industrial type sewing machines to impart a concomitant feeding motion to the workpiece by use of a puller mechanism assembly in order to assist the sewing head during the sewing operation. Attempts have been made by using pullers which include upper and lower (top and bottom) rollers which contact the fabric after sewing so as to pull the workpiece through the sewing station. As is apparent, if the puller mechanism is going to aid in advancing the workpiece it is required to move in excess of the speed of the feed mechanism of the machine. However, the excess speed requirement sometimes requires the use of additional mechanisms so as to achieve the desired ratio as well as to allow adjustment of said ratio.
Such devices known for concomitantly feeding the workpiece in relation with the feed mechanism of the machine have the disadvantage of usually requiring cumbersome supports and guides which must be situated about the sewing head so as to derive power therefrom. This leads to another disadvantage in that the higher speeds of todays machines require a minimum of loading to be placed on the machine so that quick acceleration and the higher speeds of the machine may be achieved. As mentioned above, and as is apparent the auxiliary feed mechanisms are usually set to run faster than the speed at which the feed mechanism is moving in the material workpiece so as to aid the machine feed mechanism but unless this quicker speed is calculated quite carefully undesired gathering of the material workpiece could result in excess gathering over that which is desired and therefore the ends of the workpiece may not end up equal. In this regard, the lack of an adequate adjustability factor is yet another drawback in the heretofore known devices. That is, once the speed of the auxiliary feed mechanism has been adjusted it has not been possible to vary the speeds of said mechanism during sewing. Furthermore, with the heretofore known devices the torque of the auxiliary feed mechanism has not been fully developed until the sewing machine has attained its full or required speed, whereas it is desirous to achieve full torque of the auxiliary feed mechanism as quickly as possible so as to advance the workpiece in conjunction with the speed of the feed mechanism of the machine.